Microbial products can influence immunoregulation through their effects on cellular and/or humoral components of the immune system. We have recently demonstrated a new immuno-modulator - staphylococcal peptidoglycan (PG). PG is a B cell mitogen and induces polyclonal antibody synthesis in rodent and human lymphocytes. We will study polyclonal activation of murine B lymphocytes by PG and the contribution of this phenomenon to the induction of autoantibodies in normal and immunodeficient mice. We will compare the mechanism of PG and lipopolysaccharide (LPS) induced secretion of polyclonal antibodies, using the protein A hemolytic plaque assay, with special attention to: (a) requirement for DNA synthesis; (b) time of exposure required for stimulation; (c) sensitivity to suppressor cells; (d) inhibition by polymyxin B; and (e) ontogenic development of the responsiveness to PG. High proportions of PG and LPS stimulated cells secrete autoantibodies. Using the plaque assay and its modifications with protein A-, IgG, or DNA coated erythrocytes, we will determine what percentage of all PG and LPS activated cells secrete antibodies specific to: (a) autologous IgG (rheumatoid factor); (b) heterologous IgG; (c) DNA; and (d) autologous and heterologous erythrocytes. Finally, we will compare the in vivo and in vitro appearance of spontaneous and PG and LPS induced autoantibodies, their specificities, persistence, and relation to age, both in normal mice and in strains with the following inborn immune defects: (a) spontaneous autoimmune disease; (b) partial defect of B lymphocytes; and (c) lack of T lymphocytes. These studies will characterize PG as a new tool for the investigation of lymphocyte activation and induction of autoantibodies. Since autoantibodies play a major diagnostic and pathologic role in human autoimmune diseases, we will prove a new model for the studies of the role of polyclonal activators in triggering and exacerbating autoimmune diseases.